Vehicle passenger cabins may be heated using internal combustion engine waste heat that is transferred to engine coolant. Specifically, passenger cabin air and fresh air are blown across a heater core in which engine coolant circulates. Heat is transferred from the engine coolant to the cabin air and the cabin air is circulated about the cabin. However, some vehicles do not include an internal combustion engine, or the internal combustion engine may be stopped to conserve fuel so that little engine waste heat may be available to warm the passenger cabin. One way to heat cabin air within a passenger compartment of an electric or hybrid vehicle is to heat the cabin air via a heat pump. The heat pump extracts heat from ambient air outside of the vehicle and transfers the heat to air in the passenger compartment. The heat pump is operated by using electrical energy to rotate a compressor and a fan that directs air over an evaporator. If the compressor and/or fan are driven at speed that are above or below desired speeds, the heat pump may consume more energy than is desired and it may provide more or less heat than is desired to the passenger cabin. Consequently, the vehicle in which the heat pump operates may provide less driving range than is desired due to the fan and/or compressor consuming excess electrical energy from the vehicle.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating heat pump of a vehicle, comprising: increasing an evaporator cooling fan input power by a first amount to a first input power and maintaining the evaporator cooling fan input power at the first input power in response to compressor input power decreasing by more than the first amount.
By weighing adjusting in evaporator fan power in response to compressor output power, it may be possible to provide the technical result of ascertaining whether or not it is beneficial to adjust evaporator fan input power to conserve energy used to operate a heat pump while providing a desired level of cabin heat. In particular, if increasing evaporator fan input power allows compressor output power to be reduced by an amount that is greater than the increase of evaporator fan input power speed while providing a desired level of cabin heat, the evaporator fan input power is increased. Otherwise, the evaporator fan input power may be maintained.
The present description may provide several advantages. Specifically, the approach may improve heat pump operating efficiency. Further still, the approach may extend vehicle driving range. Further still, the approach may provide a desired level of cabin heating while extending vehicle driving range.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.